That's an awesome tip! I know you used to be able to do it using a key combo that included the left and right square bracket keys. That always seemed awkward, and this way (cmd-opt-L/R) is a lot easier.

I often have 20 or more tabs open. As to why...throughout the course of the day, I open tabs for one reason or another--sometimes personal interests, sometimes work-related. But I don't always have time to look at them to the degree I want, so I leave them open as a reminder to look at them.